Thermal abatement systems

ABSTRACT

A thermal abatement system comprises an axial inlet, radial outlet supercharger. A main case comprises at least two rotor bores, an inlet plane and an outlet plane. The inlet plane is perpendicular to the outlet plane. An inlet wall comprises an inner surface. Two rotor mounting recesses are in the inner surface, and the inlet wall is parallel to the inlet plane. An outlet is in the outlet plane. An inlet is in the inlet plane. At least two rotors are configured to move air from the inlet to the outlet. The main case comprises at least two backflow ports. An intercooler is connected to receive air expelled from the supercharger, to cool the received air, and to expel the cooled air to the at least two back flow ports.

PRIORITY

This application is a continuation of U.S. Ser. No. 14/699,113 filedApr. 29, 2015, which claims priority under 35 USC 365(c) to, and is acontinuation-in-part of, PCT/US2014/063439 filed Oct. 31, 2014.PCT/US2014/063439 filed Oct. 31, 2014 claims priority to U.S.provisional patent application 61/897,928 filed Oct. 31, 2013, U.S.provisional patent application 61/991,166 filed May 9, 2014, US Designpatent application 29/499,660 filed Aug. 18, 2014, and Indianprovisional patent application 2337/DEL/2014 filed Aug. 18, 2014. U.S.Ser. No. 14/699,113 filed Apr. 29, 2015 claims priority to U.S.provisional patent application 61/986,081 filed Apr. 29, 2014. Each ofthe priority applications is incorporated herein by reference in theirentirety.

TECHNICAL FIELD

The present disclosure relates generally to a supercharger system. Morespecifically, a supercharger system achieving a high pressure ratio andlow outlet temperature by backflowing cooled air from an intercooler tothe supercharger.

BACKGROUND

A supercharger can be implemented to supply compressed air to acombustion engine. When the air is compressed, then more air can besupplied, enabling a vehicle to produce more power. There are differentkinds of superchargers available, including Comprex, Roots type,twin-screw, and centrifugal. They differ in the way that air iscompressed and moved to the intake manifold of the engine.

The Roots type supercharger is a positive displacement pump that forcesair around the outer circumference of rotors and blows the air into themanifold. Therefore, a Roots type supercharger is sometimes called a“blower.” More specifically, the Roots type supercharger has twocounter-rotating lobed rotors. The two rotors trap air in the gapsbetween rotors and push it against the housing as the rotors rotatetowards the outlet/discharge port into the engine's intake manifold. Bymoving air into the manifold at a higher rate than the engine consumesit, pressure is built.

Because of its simple design, the Roots type supercharger is widelyused. However, the Roots type supercharger has some disadvantages. Whenthe chamber of trapped air is opened to the engine's intake manifold,the pressurized air in the engine's intake manifold reverse-flowsaccording to thermodynamic and fluid mechanic principles into thesupercharger. Further, there could be a leakage of air between therotors due to gaps, or leakage due to gaps between the rotor lobes andhousing, the gaps supplied for thermal expansion tolerances. Bothreversion of air and air leakage contribute to the thermalinefficiencies of the Roots type supercharge. And, due to its nature toproduce high discharge temperatures, it can take away from the engineperformance. For example, when the temperature of discharged air isincreased, it can cause detonation, excessive wear, or heat damage to anengine.

In many positive displacement compression devices, such as reciprocatingcompressors, the pressure is increased by reducing the volume occupiedby gas. For example, a piston physically compresses a large volume ofgas into a smaller volume to increase pressure. However in a Rootsdevice there is no mechanism like a piston to compress the gas. TheRoots blower scoops the air from a low pressure suction side and movesthis air to the high pressure outlet side. When the low pressure airscooped by the Roots supercharger comes in contact with the highpressure outlet side, then a backflow event takes place whereby the highpressure gas from the outlet backflows into the supercharger to compressthe low pressure gas into higher pressure gas. Thus the compression ofgas in the supercharger happens through this backflow event. This alsoheats up the compressed low pressure gas to a higher temperature basedon thermodynamic principles. After compression of the gas, the blades ofthe Roots supercharger squeeze the compressed air out of thesupercharger into the high pressure outlet side.

Typically, Roots superchargers use hot high pressure air available atthe outlet for the backflow event. However, it is possible to cool theRoots compressor by using relatively colder high pressure gas availableafter the intercooler. But, issues remain to determine the backflow slotsizing, placement, and geometry necessary to get an optimum backflowevent that provides the lowest operating temperature for thesupercharger while providing the highest operating efficiency.

SUMMARY

In an effort to increase boost, which is given in terms of pressureratio to the engine, a high pressure ratio is needed. Pressure ratiodenotes the ratio of absolute air pressure before the supercharger tothe absolute air pressure after the compression inured by thesupercharger. At higher pressure ratio, or boost, more air mass isdelivered to the engine allowing a greater amount of fuel to be burnt aswell resulting in higher power output.

A thermal abatement system comprises an axial inlet, radial outletsupercharger. A main case comprises at least two rotor bores, an inletplane and an outlet plane. The inlet plane is perpendicular to theoutlet plane. An inlet wall comprises an inner surface. Two rotormounting recesses are in the inner surface, and the inlet wall isparallel to the inlet plane. An outlet is in the outlet plane. An inletis in the inlet plane. At least two rotors are configured to move airfrom the inlet to the outlet. The main case comprises at least twobackflow ports. An intercooler is connected to receive air expelled fromthe supercharger, to cool the received air, and to expel the cooled airto the at least two back flow ports.

A thermal abatement system comprises an axial inlet, radial outletsupercharger. A main case comprises at least two rotor bores, an inletplane and an outlet plane. The inlet plane is perpendicular to theoutlet plane. An inlet wall comprises an inner surface. Two rotormounting recesses are in the inner surface, and the inlet wall isparallel to the inlet plane. An outlet is in the outlet plane. An inletis in the inlet plane. At least two rotors are configured to move airfrom the inlet to the outlet. The main case comprises at least twobackflow ports. An intercooler is connected to receive air expelled fromthe supercharger, to cool the received air, and to expel a selectiveportion of the cooled air to the at least two back flow ports. An engineis connected to receive another portion of the cooled air from theintercooler, and the engine is configured to combust the cooled air andto expel exhaust. An exhaust gas recirculation (EGR) conduit isconnected to selectively receive a portion of the exhaust and is furtherconnected to input the exhaust back in to the thermal abatement systemfor additional combustion.

It is to be understood that both the foregoing general description andthe following detailed description are exemplary and explanatory onlyand are not restrictive of the invention, as claimed.

BRIEF DESCRIPTION OF THE DRAWINGS

The accompanying drawings, which are incorporated in and constitute apart of this specification, illustrate several examples of the presentteachings and together with the description, serve to explain theprinciples of operation.

FIG. 1A is a schematic view of a supercharger system with cooled airbackflow conduits.

FIG. 1B is a schematic of a supercharger system with cooled air backflowconduits and having an air bypass conduit.

FIG. 1C is a schematic of a supercharger system with combined airbackflow and air bypass conduits.

FIGS. 2A-2F are examples of control systems.

FIG. 3 is a graph showing pressure ratios.

FIG. 4A is a simulation result showing the temperature distribution of asupercharger without backflow of cooled air.

FIG. 4B is a simulation result showing the temperature distribution of asupercharger with backflow of cooled air.

FIG. 5 is an example of a Roots type supercharger.

FIG. 6A-6D are views of a supercharger main case.

FIG. 7 is a view of an alternative supercharger main case.

FIG. 8 is a view of air transfer between lobes.

FIG. 9 is an alternative view of air transfer between lobes.

FIG. 10 is a comparison of phase diagrams for lobe timing.

FIG. 11A-D are flow diagrams for thermal abatement systems comprising asupercharger boosting a turbocharger.

FIGS. 12A and 12B are flow diagrams for thermal abatement systemscomprising a turbocharger boosting a supercharger.

FIGS. 13A and 13B are flow diagrams for thermal abatement systemscomprising a supercharger boosting another supercharger.

DETAILED DESCRIPTION

Reference will now be made in detail to the present exemplary aspects ofthe present teachings, examples of which are illustrated in theaccompanying drawings. Wherever possible, the same reference numberswill be used throughout the drawings to refer to the same or like parts.Bold arrow-headed lines indicate air flow direction, unless otherwisenoted.

FIG. 1 shows a supercharger system 10 for controlling the outletcondition of a supercharger 100 through conditioning of the backflowair. Supercharger 100 can have an air inlet 101, a chamber 105, and anoutlet 104. The supercharger system 10 is a backflow control system forcontrolling the backflow event to adjust the temperature at the outlet104 of the supercharger 100. Supercharger 100 is a positive displacementair pump, and can be a Roots type, or a different type such as a screwtype. When actively blowing, or pumping, air, the supercharger 100 heatsair as it passes through the chamber 105. Supercharger 100 is used tocompress air going to a combustion engine 120 and to increase the poweroutput of the engine. Compression can happen as a result of highpressure outlet air back flowing into the low pressure control volume ofair as the control volume is transferred to the outlet. The system 10includes mechanisms for introducing cooled outlet air instead of hotoutlet air for the backflow event.

The introduction of cooled air during backflow increases the pressureratio of the supercharger system over prior art methods. The pressureratio describes the amount of boost the supercharger can supply to theengine, and is the ratio of the fluid pressure before the superchargerto the fluid pressure after the supercharger. A gas, such as ambientair, is the preferred fluid for compression, though, at times, an amountof other fluid, such as exhaust, can be present due to Exhaust GasRecirculation (EGR).

Currently, the pressure ratio of a Roots supercharger is limited by themaximum operating temperature, or thermal limit, of the device. Thethermal limit is determined by factors such as oil degradation, thermalexpansion of metal parts such as the rotor and/or housing, operationalfatigue, and durability issues. By reducing the temperature of fluidcirculating in the supercharger, the pressure ratio of the device canincrease while staying within the thermal limit of the device.

Generally, to reduce the temperature of air going into the engine, anintercooler is used to cool the air from the supercharger. The reductionof air temperature will increase the density of the air, whichconsequently increases the engine's ability to make more horsepower andtorque. By backflowing cooled air from the intercooler to thesupercharger, the pressure ratio of the supercharger increases whilereducing the temperature of the discharged air from the supercharger100.

In FIG. 1, the air inlet 101 allows ambient air to come into thesupercharger 100. The air inlet 101 is located on the tubular housing inan inlet plane IP at an inlet side of the supercharger 100. The inlet101 can comprise a crescent shape or other shape. An outer edge of theinlet 101 shape can be parallel to, or congruous with, the shape of therotor bores. The chamber 105 can comprise two rotor bores containing tworotors 102, 103. Each rotor rotates about an axis parallel to a firstaxis, or inlet axis IA. Each rotor can have at least two lobes, butpreferably, three or four. Rotor 102 has three lobes, 102A, 102B, and102C. Similarly, rotor 103 has three lobes, 103A, 103B, and 103C. Thelobes can be parallel or twisted. For an example of the twisted design,the rotors can be either hi-helix type or standard helix type. Hi-helixis sometimes characterized as a 120° rotor, while a standard helix issometimes characterized as a 60° rotor. Each degree indicates the amountof rotor twist over the length. Other degrees of twist can be used basedon the design, from zero degrees (parallel lobes) up to 170°, with anexemplary twist range of 60-150 degrees.

For example, FIG. 10 compares a first example and a second example ofphase diagrams and port timings for two exemplary superchargers. Inexample 1 on the left, the supercharger has two three-lobe rotors of thefifth generation, GEN V, style manufactured by Eaton Corporation. Thelobes are twisted 60 degrees along their length. The phase diagram forexample 1 indicates the rotational travel for each lobe of the rotor. Agiven lobe travels 210 degrees of rotation to complete the inlet phase,where air is drawn in through the inlet 1011 or 1012. The lobe thentravel 50 degrees to complete the dwell phase and 40 degrees to completethe sealed phase. The backflow event is allotted 40 degrees of lobetravel, and the outlet, or exhaust, phase is allotted 200 degrees oflobe travel to blow the air out of the supercharger. By designing thebackflow ports 122 and 1222 to be smaller than the allotted lobe travel,the transfer volume can experience an abrupt and lengthy backflow event.For example, the axial flow back flow slot 1222 can be designed to openin 10 to 15 degrees of rotor rotation, thereby yielding a lengthy cooledair backflow event.

Example 2 of FIG. 10 uses a supercharger with two four-lobe rotors. Thelobes twist 160 degrees along their length. The inlet phase time isincreased to 280 degrees, and the outlet phase time is increased to 220degrees. The dwell phase is reduced to 20 degrees and the seal phasetime is decreased to 10 degrees. The backflow event time is increased to80 degrees. If the axial flow backflow port 1222 remains as above, madeto open within 10 to 15 degrees of lobe rotation, the cooled airbackflow event is further increased in duration. If a larger axial flowbackflow port is used, such as a fully circular port, the port would notopen as abruptly or remain fully open for the full backflow phase. Inthe case of the circular port, if it is sized to close completely vialobe blockage, it would take 30-40 degrees of lobe rotation tocompletely open the circular port.

Table 1 summarizes exemplary timing ranges available for twisted lobeGen V (Fifth Generation) and TVS® (Twin Vortices Series) superchargersmanufactured by Eaton Corporation. For a given lobe phase, the generaltiming range is given and is contrasted against six other timingscenarios for exemplary superchargers.

TABLE 1 Example Example Example Example Timing Example Example 3 Timing4 Timing 5 Timing 6 Timing Lobe Range 1 Timing 2 Timing Ranges RangesRanges Ranges Phase (Degrees) (Degrees) (Degrees) (Degrees) (Degrees)(Degrees) (Degrees) Inlet 210-280 210 280 210-280 210-280 210-280210-280 Dwell 20-50 50 20 20-50  0-50 20-50 20-50 Seal 10-70 40 10 20-4015-70 10-50 15-45 Backflow 20-80 40 80 25-50 20-70 20-80 20-50 Outlet200-220 200 220 200-220 200-220 200-220 200-220

For enabling abrupt opening and closing of the backflow port, it isadvantageous to shape the port akin to the lobe shape. So, turning toFIG. 8, the upper axial flow back flow port 1222 is shown aligned withthe lobe 102A. Because the port is “bean” shaped to substantially matchthe profile of the lobe, in this instance, match a segment of the outercurve of the lobe, the port does not suffer leakage of air in to theoutlet volume 140E or in to the transfer volume 140S. Rather, the lobesare able to block cooled air transfer to seal against parasitic leakageof air. This is beneficial to prevent not only leakage of air back tothe inlet volume 140I, but also to prevent outlet air from leakingbackwards through the back flow ports. While it is permissible to leakcooled air to the outlet volume 140E, it is desired to limit squeeze ofoutlet air back through the back flow ports. It is possible with the“bean” shape to prevent leakage between the axial inlet backflow port1222 and the outlet 104. It is possible with this design to limit cooledair backflow to the designated backflow volume 140B at the designatedphase, as shown in FIG. 9. Thus, the axial flow back flow port 1222 is aslot designed to have a profile matching a segment on an involute curve.The slot can have rounded edges for smoothed air flow profile. The “beanshaped” slot can be described as a slot having four sides, each sidebeing an arc of a circle. Alternatively, the axial flow back flow port1222 is a rectangular slot, an oval hole, or a circular hole sized toopen fully in 10 to 40 degrees of lobe rotation and sized to be fullyobstructed by the lobe when the lobe is aligned over the hole. Theradial flow back flow ports 122 are likewise designed to open and closeabruptly, and this is accomplished via slots having rectangular, oblong,or other shapes matching the twist of the lobes along their axiallengths.

Rotors 102, 103 can be identical to each other. Or, lobes 102A, 102B,102C of rotor 102 can be twisted clockwise while the lobes 103A, 103B,103C of rotor 103 can be twisted counter-clockwise. For the examples ofFIGS. 1, 5, and 8-10, because rotors 102, 103 have twisted lobes, thesupercharger 100 can have much better air handling characteristics.Further, the supercharger 100 can produce less air pulsation andturbulence. The length of rotors 102, 103 can vary among applications.The size of the supercharger 100 can be determined by the length ofrotors 102, 103. Rotors 102, 103 can be meshed together along the firstaxis, inlet axis IA, as the rotors rotate, and the rotors can be gearedto rotate in opposite directions.

The air entering into the chamber 105 of supercharger 100 can be trappedin a gap between adjacent lobes of rotor 102, for example, between lobes102A and 102B. The air can also be trapped in a gap between adjacentlobes of rotor 103, for example, between lobes 103A and 103B. Thetrapped air can be carried to an outlet 104 to be expelled out of thesupercharger 100. In the examples shown, the supercharger is anaxial-inlet, radial-outlet type supercharger. This means that the inletair travels into the tubular housing along the axis of the rotors,parallel to the inlet axis IA. As the rotors rotate, the air movesradially away from the inlet axis IA and towards the outlet 104, whichis in an outlet plane OP perpendicular to the outlet axis OA. The inletaxis IA and the outlet axis OA are perpendicular. The outlet 104 can bea triangular shape to match the shape of the rotors 102, 103, or anothershape that allows for an easy exit of air. Since the volume oftransferred air can be greater than the displacement of engine 120, theair pressure within engine 120 can be increased. In other words, theRoots type supercharger 100 can produce boost pressure by stacking moreand more air into the intake manifold.

An intercooler 110 can comprise an inlet port 113, an outlet port 111,and a recirculation conduit 112. Each rotor 102, 103 can have anaffiliated recirculation conduit 112 so that cooled air is fed back tothe supercharger in a balanced manner. The inlet port 113 can beconnected to the outlet 104 of the supercharger 100 to receive thedischarged air. The intercooler 110 can be any mechanical device thatacts as a heat sink. Further, the intercooler 110 can comprise a bar, aplate core, and fins (not shown in figures). Once the discharged airfrom the supercharger 100 enters the intercooler 110, air can movethrough bar and plate core to make its way to the outlet port 111, whilebecoming cooled through heat transfer. General details of the workingmechanics of an intercooler are well known, and thus, will not bedescribed herein. The intercooler 110 can vary dramatically in size,shape and design depending on the performance and space requirements ofthe supercharger system. Intercooler 110 can be air-to-air type orair-to-water type.

The outlet port 111 expels the cooled air towards an intake manifold ofengine 121 and the outlet port 111 can be connected to conduits 112 byway of optional valves 114A and valve sensor and actuation devices 114.The conduits 112 can branch out either to left, right, or both sides ofthe outlet port 111. The other end of the conduit 112 connects to radialflow backflow ports 122 of supercharger 100 such that cooled air can betransferred between lobes of the rotors. Alternative examples enableconduit connectivity to the axial flow backflow ports 1222 alone or incombination with the radial flow back flow ports 122.

Some supercharger systems utilize back flow ports to reduce noise comingfrom the supercharger. Instead of receiving hot outlet air back flow, itis possible to use the radial flow back flow ports 122 for receivingcooled air from conduits 112. This can reduce the noise stemming fromthe operation of the supercharger. Therefore, having conduits 112 canimprove noise, vibration, and harshness (NVH) capabilities of thesupercharger.

It may be necessary to adjust the size, shape, and location of theradial flow and axial flow backflow ports 122, 1222 shown in the Figuresto provide optimal cold air input to the supercharger. The cold airradial flow backflow ports 122 of FIG. 5 are located on the main case106 after the inlet 101 and before the outlet 104. That is, the radialflow backflow ports 122 are distinct from the inlet 101 and the outlet104. The radial flow backflow ports 122 can align with the gaps betweenthe lobes of the rotors such that as the rotors spin, the cooled air ismixed with intake air in a gap as the gap passes the radial flowbackflow port 122. To ensure proper mixing, a distance between the inletand a radial flow backflow port is greater than a distance between a gapand its adjacent backflow port. As shown in FIG. 5, the radial flowbackflow port can be closer to the outlet than to the inlet.

The radial flow and axial flow back flow ports 122, 1222 are sized andshaped to introduce the cooled backflow air between the rotors at alocation where the rotors form a “sealed volume.” That is, the rotorsrotate to move air from the inlet to the outlet of the supercharger, andthere is a point where the gap between lobes is sealed from both theinlet and the outlet. Cooled backflow air is introduced in to this gap,or sealed volume, by the strategic placement, shape and number of radialflow and axial flow backflow ports 122, 1222.

For example, two radial flow back flow ports 122 may be used, asillustrated in FIG. 5, or one may be used, as illustrated in FIGS. 6A-9.The radial flow back flow ports 122 can be rectilinear or rounded, asillustrated, or another tunable shape, such as oval or circular.Preferably, the shape of the ports allows a sharp opening and closing ofthe ports, such that the backflow event occurs abruptly at a very highrate. The number of axial and radial flow back flow ports is selectableto augment the tuning of the cooled air backflow.

Inlet side axial flow backflow ports 1222 encourage axial flow of thecooled, high pressure backflow air by being positioned on the inlet sideand at a location that causes cooled air to be drawn from the lowerpressure, lower temperature inlet side to the high pressure, hightemperature outlet side of the supercharger. The trajectory of thebackflow air at the inlet side axial flow backflow ports 1222 is alongthe inlet axis IA, and so the high pressure cooled air rushes along therotor length, as shown by the bold arrow in FIG. 9. Thus, the inlet sideaxial flow backflow ports 1222 complement the axial-inlet, radial-outletdesign of the supercharger.

The cooled air backflow can be performed with only the inlet-side axialflow backflow ports 1222, with only the outlet-side radial flow backflowports 122, or with a combination of inlet-side axial flow backflow ports1222 and outlet-side radial flow backflow ports 122. Thus, the number ofbackflow ports can vary from two, one for each rotor, to six, yieldingthree ports for each rotor. If the ports are made smaller, a greaternumber of ports per rotor can be implemented.

As shown in FIGS. 6A-7, the radial flow backflow ports 122 can bereduced from four to two on the outlet 104 side of the main case 106.Axial flow backflow ports 1222 are added to an inlet wall 1063 on theinlet 104 side of the main case. Inside the main case 106, an inner sideof the inlet wall 1063 includes rotor mounting recesses 1020 and 1030that intersect a plane parallel to the inlet plane IP. In anotheralternative, the main case comprises the axial flow backflow ports 1222and does not include any radial flow backflow ports 122.

The tubular main case 106 includes a front plate 1060. In FIG. 6A, thefront plate 1060 includes a machining pass-through 1061 to permittooling access to the axial flow backflow ports 1222. The pass-through1061 receives a plug to seal the front plate 1060 after machining.Alternatively, a recirculation conduit 112 is coupled to thepass-through 1061 to encourage axial backflow air flow with reducedreflection of air waves. To facilitate conduit coupling, thepass-through can be other shapes than the illustrated “mushroom” shape,such as circular, oval, rectangular, or square. FIG. 7 eliminates thepass-through 1061 in favor of a sealed front plate 1060.

A tuning distance TD between the inlet wall 1063 and front plate 1060 isselected to permit backflow air to couple to the axial flow backflowport 1222 without creating excessive standing waves or reflections ofair back out of the chamber 105. The tuning distance TD is selected tolimit flow losses and to control air restriction in to the axial flowbackflow ports 1222. Additional control of the flow is determined by thelength and diameter of the recirculation conduit 112 between theintercooler and the backflow compartment 1075. The backflow compartment1075 can include the volume of air exposed to the radial flow backflowports 122 and the volume of air exposed to the axial flow backflow ports1222. The at least one divider 1062 cooperates with walls 1064, 1065 ofthe tubular housing and with the front plate 1060 to form backflowcompartment 1075.

Inlet 101 optionally includes a support 1010. Inlet 101, as above,supplies intake or bypass air to the rotors 102, 103 of thesupercharger. The support 1010 provides an indicator in FIG. 6C for thehalves of the inlet. Inlet area 1011 is allocated for rotor 103, andinlet area 1012 is for rotor 102. The inlet 101 can be described asextending for an amount of the tubular housing. But, it is convenient todefine the inlet for each rotor such that inlet area 1012 has an inletextent Θ_(I) in a circular area of the inlet wall 1063 allocated forrotor 102. Using this convenient reference, the inlet face is divided into 360 degrees about a center point at vertex V in the rotor mountingrecess 1020. The transfer or seal extent Θ_(S) occupies another portionof the inlet wall 1063. The axial flow back flow port 1222 occupies abackflow extent Θ_(B), and the remainder of the circular area is forrotor travel to accommodate the outlet phase and rotor meshing. A mirrorimage of the angular extents is applicable to the rotor mounting recess1030 utilizing a vertex V2 and inlet 1012.

The use of the vertices V, V2 divides the inlet plane to explain thelocations for the axial flow back flow ports 1222 with respect to theinlet 104. Depending upon whether the rotors comprise 3, 4, or 5 lobes,and depending upon the twist of the lobes being 60-150 degrees, theinlet area 1011 occupies an extent Θ_(I) in the inlet plane. So whilethe timing requires a large rotation angle for the twisted lobe to passthe inlet area 1011, the angular extent of the inlet area Θ_(I) can besmaller than the degree of the timing. Inlet extent Θ_(I) can beapproximated by adding the rotor twist angle to the dwell phase of Table1, for a range of 80-200 degrees.

Seal extent Θ_(S) can be approximated by adding the seal phase of Table1 to the lobe spacing. Depending upon whether the lobes are spaced 72,90, or 120 degrees apart, or another spacing, and using a seal phase of10-70 degrees, the seal Θ_(S) would be in a range from 82-190. As above,the axial flow back flow port 1222 opens or closes in 10-40 degrees oflobe rotation, and so the backflow extent Θ_(B) is approximated tooccupy 10-40 degrees of the inlet plane about the vertex V. The inletarea 1011 is thus separated from the axial flow back flow port 1222 byapproximately 82-190 degrees. Table 2 offers additional examples forexplaining the location of the axial flow back flow ports 1222.

TABLE 2 Angle of Angle of Angle of Inlet Inlet Inlet Angle of InletAngle Range Plane Plane Plane Plane of Inlet Plane Occupied OccupiedOccupied Occupied Occupation Example 1 Example 2 Example 3 Example 4θ_(I) 80-200  80 170 110 200 θ_(S) 82-190 100 170 140 170 θ_(B) 10-40 10-40 10-40 10-40 10-40

Inlet 101 is sealed from the backflow volume in integrated manifold 1070via a floor 1071. The floor can be an inserted seal or part of thehousing casting. The support 1010 couples to floor 1071 of integratedmanifold 1070. The floor 1071 is between the inlet wall 1063 and thefront plate 1060 and forms the integrated manifold 1070 in cooperationwith extensions of walls 1064 and 1065. Floor 1071 fluidly separates theinlet 101 from the axial flow back flow ports 1222 by providing physicalseparation between inlet 101 and integrated manifold 1070. Inlet airthus cannot mix with cooled backflow air.

The inlet 101 extends through the front plate 1060 and intersects aninlet plane IP along inlet wall 1063. The axial flow backflow ports 1222are also in the inlet plane IP. The inlet plane IP is perpendicular tothe inlet axis IA, which is shown coming out of the page in FIG. 6C.

The outlet 104 and, when used, the radial flow back flow ports 122, arein an outlet plane OP that is perpendicular to the inlet plane IP. Theoutlet plane is also parallel to the inlet axis IA. An outlet axis isshown coming out of the page in FIG. 6B. The outlet axis isperpendicular to the inlet axis IA and is perpendicular to the outletplane OP, as in FIG. 6A. When describing the supercharger as an axialinlet, radial outlet device, it is convenient to explain that airtravels in to the supercharger inlet 101 and through the axial flowbackflow ports 1222 axially, or along the rotor axis, which are parallelto inlet axis IA. As the supercharger acts on the inlet air and thebackflow air, the air is directed to leave the outlet 104 radially withrespect to the rotor axis, meaning the air exhausts along, or generallyparallel to, the outlet axis OA. This differentiates the superchargerfrom radial inlet, radial outlet devices, which do not have the same airflow characteristics or leakage constraints.

A tuning distance TD separates the front plate 1060 from an inlet wall1063 of the main case 106. The tuning distance TD is selected toregulate the flow of cooled backflow air to the axial flow backflowports 1222. The alignment of the integrated manifold 1070 with the axialflow backflow ports 1222 is selected to direct the air flow in to thechamber 105 in the direction of the outlet 104. By directing the flow,the supercharger works less, compared to the radial flow backflow ports122, to blow the air out because the air flows axially along the rotoras the rotor spins in the chamber 105.

Referring to FIGS. 8 and 9, the cooled backflow air exits theintercooler 110 and is directed to the backflow compartment 1075. Thelobes 102A-102D and 103A-103D are twisted along the length of theirrespective rotors and are hollow, as indicated by the hollows 102H and103H. Looking to FIG. 8, lobe 102B and 102C are exposed to the inlet 101and permit an inlet volume 140I of air to enter the main case 105. Lobe102D is sealed against the main case 105. Lobe 102A also seals againstthe main case 106 and blocks its affiliated axial flow backflow port1222 and blocks its affiliated radial flow backflow port 122. A sealedtransfer volume 140S is formed between lobes 102A and 102D. An exitvolume 140E of air is exposed to the outlet 104 between lobes 102A and102B.

When the rotor 102 rotates additionally, as shown in FIG. 9, lobe 102Ano longer blocks axial flow backflow port 1222 and no longer blocksradial flow backflow port 122. Cooled backflow air can now enter the gapbetween lobes 102A and 102D. Ideally, though not required, the transfervolume is still sealed from the inlet and from the outlet, but thesealed transfer volume 140S of air mixes with the cooled backflow air toform a backflow transfer volume 140B. As the inlet air moves from theinlet to outlet, the inlet air is heated. The cooled backflow airfollows thermodynamic principles, moving from low temperature to hightemperature and from high pressure to low pressure, thereby progressingfrom the inlet end of the rotor 102 to the outlet 104. The result is agreater amount of air blown by the supercharger between lobes 102A and102D.

The rotors 102, 103 of FIGS. 8 and 9 are meshed and oppositely rotating,and the timing of the rotors is such that rotor 103 is exposed to cooledbackflow air input at different times than rotor 102. So, when rotor 102blocks axial flow backflow port 1222, rotor 103 exposes the gap betweenlobes 103A and 103B to cooled backflow air to create a backflow transfervolume 141B. Rotor 103 blocks its axial flow backflow port 1222 whenrotor 102 has fully exposed its axial flow backflow port 1222. Theextent of blockage or exposure is determined by the shape and size ofthe lobes 102A-102D, 103A-103D and by the shape, location, and size ofthe axial flow and radial flow backflow ports 122 and 1222.

As illustrated in FIG. 8, the shape and orientation of the lobes102A-102D, 103A-103D and the shape and orientation of the axial flow andradial flow backflow ports 122 and 1222 complement one another. Thecomplementary pairing permits the tuning of sealing and timing. Thus thesealed transfer volumes open to the backflow transfer volumes atdistinct points as the lobes pass the backflow ports. As above, the useor non-use of the axial flow or radial flow backflow ports with oneanother permits additional tuning of the backflow characteristics andthus the compression ratio of the supercharger.

Thus, for customer compression ratio demands, a system can be designedto operate a supercharger at an ideal rotor speed to achieve an idealcompression ratio, and the size, orientation, and timing of the lobesare selected to complement the use of one or both axial flow and radialflow backflow ports to further tailor the achievement of the targetcompression ratio. Greater control of standing waves inside the chamber105 is achieved. Greater control over exit pulsations is achieved.

As an additional point of air flow tailoring, the length and diameter ofthe input 101 is selected to impact the length of standing waves in thechamber 105. Thus, not only the tuning distance TD of the integratedmanifold 1075 is controllable, but the input 101 length is alsocontrollable.

At least one divider 1062 separates the outlet 104 from the backflowcompartment 1075. The outlet 104 and divider 1062 can mate with ductingfor communicating air with an intercooling device. And the divider 1062and backflow compartment 1075 can mate with the recirculation conduit112.

The width of the intercooler outlet port 111 can be designed to meet theneed of a particular supercharger in consideration of size, type, andspace, along with other performance requirements. For example, the widthof outlet port 111 can be much wider than the width of the radial flowbackflow port 122. As an example, the width of the outlet port 111 canbe 43 mm while using the width of a single backflow conduit 112 of 8 mm.In other designs, the radial flow and or axial flow backflow port andaffiliated conduit can have a greater cross-sectional area than theoutlet port 111 and its affiliated conduit. The port and conduit sizesare adjusted for particular applications to ensure fluid flow fromsupercharger outlet, to intercooler, to backflow port. Thus,thermodynamic laws for pressure and temperature impact backflow portlocations and sizes so that cooled air exiting the intercooler 110 canbackflow via the conduit 112 back to the supercharger 100.

As one example, the size of the radial flow and axial flow backflowports 122, 1222 is determined by the below estimation of the port areaA_(Port):

$A_{Port} = \frac{\frac{\left( {{\frac{P_{2}}{{RT}_{2}}V_{TransferVolume}} - {\frac{P_{1}}{{RT}_{1}}V_{TransferVolume}}} \right)}{\left( {\frac{{Angle}\mspace{14mu}{for}\mspace{14mu}{{Backflow} \times 60}}{360}/N_{RPM}} \right)}}{\frac{P_{2}}{{RT}_{2}}\frac{a_{1}}{\gamma}\left( {\frac{P_{2}}{P_{1}} - 1} \right)\left( \frac{\frac{2\gamma}{\gamma + 1}}{\frac{P_{2}}{P_{1}} + \frac{\gamma - 1}{\gamma + 1}} \right)^{\frac{1}{2}}}$where P₁ is the inlet pressure, P₂ is the maximum pressure ratio of theoutlet, T₁ is inlet temperature, T₂ is outlet temperature, R is a gascoefficient, N_(RPM) is the maximum speed in rotations per minute(“RPM”) of the supercharger, V_(TransferVolume) is the volume of airtransferred, a is the speed of sound at the given inlet temperature T₁,γ is a ratio of specific heat at a constant pressure and constantvolume.

Port area A_(Port) determines what total area should be allocated forthe cooled backflow air transfer. Thus, the sum of areas allocated tothe axial flow backflow ports 1222 and or radial flow backflow ports 122should total the port area A_(Port). The ideal port area A_(IPort) is inthe range of one fourth (¼) to 4 times A_(Port). More specifically, theideal port area A_(IPort) is one half (½) to 2 times A_(Port). Morespecifically, the ideal port area A_(IPort) is two thirds (⅔) A_(Port).

Because the axial flow back flow ports 1222 encourage axial air flowtowards the outlet 104, it is advantageous to allocate all, or most, ofthe port area A_(Port) to these backflow ports. Thus, in considerationof the timing constraints, the axial flow back flow ports 1222 shouldcomprise as much port area A_(Port) as feasible, even in favor ofomitting the radial flow back flow ports 122. But, if additional area isneeded to meet the port area A_(Port) while meeting the above 10-15degree to 30-40 degree lobe rotation for opening the axial flow backflow ports 1222, then that additional area should be allocated to theradial flow back flow ports 122. When an especially large port area isrequired, it can be necessary to include multiple radial flow back flowports 122, as illustrated in FIG. 5. When the inlet area is physicallyconstrained in an installation, it can be necessary to omit the axialflow backflow ports 1222 in favor of utilizing only radial flow backflowports 122. Thus, there can be one or more sets of backflow ports to meetdesign constraints. The one or more backflow ports are distributed toeffectuate cooling of the backflow volume 140B while preventing leakageof air back to the inlet, minimizing squeeze from the outlet 104, andpermitting abrupt opening and closing of the backflow ports.

By way of example, for a supercharger having only axial flow backflowports 1222 and no radial flow backflow ports 122, cooled backflow airenters the sealed transfer volume 140S to form backflow transfer volume140B. The integrated manifold 1075 seals the low pressure inlet air fromthe higher pressure cooled backflow air volume. The cooled backflow airenters the axial flow backflow ports 1222 parallel to the rotors and inthe direction of the air discharge at outlet 104. The lobes of rotors102 and 103 are configured as in FIGS. 8 and 9 to prevent a “shortcircuit” between the inlet volumes 140I, 141I and backflow transfervolumes 140B, 141B. That is, the cooled backflow air cannot communicatewith the inlet 104 because the lobes are sealed to prevent the backflowair from reaching the inlet 104. As illustrated, it is desired to have asealed transfer volume 140S, 141S that does not communicate with theinlet 104 or outlet 105 prior to the backflow of cooled air. While it ispossible to permit some connection between the backflow transfer volume140B and the outlet volumes 104E, 141E, in this example, the inlet,backflow, and outlet air volumes are independent of one another. A sealtime of 15-45 degrees, a backflow angle of 20-50 degrees, and a rotortwist of 60-130 degrees is applied.

In addition to adjusting the width of the radial flow and axial flowbackflow ports 122, 1222, it is possible to adjust the length of thebackflow conduit 112 to tune the flow back in to the supercharger. Thelocation of the radial flow and or axial flow backflow port is selectedto inject cooled air in to the supercharger to cool the air mass. Theideal location to inject the air is in to a sealed volume betweenrotating lobes of the rotor. That is, the rotors are in a location thatseals the injected air mass from the inlet and from the outlet. Totailor the cooling effect, the amount of air moved back to thesupercharger lobes must be controlled. Air injected between lobes of thesupercharger is tailored by selecting the length and width of thebackflow ports, thus tuning the flow. Additional tailoring is achievedby controlling the volume of the flow, as by valves, discussed below.

By backflowing the cooled air and mixing the same with the air input tothe supercharger 100, the air will be more tightly stacked in the intakemanifold 121. The pressure ratio will be higher than stacking the airnot mixed with the cooled air. In other words, by using cold highpressure air from the outlet 111 of the intercooler, the temperatureinside the supercharger 100 can be reduced. Thus, a higher pressureratio can be achieved. Therefore, without increasing the size of thesupercharger 100, greater boost is provided to engine 120.

In addition, since the cooled air is mixed with the air in thesupercharger, the resulting air transported out of the supercharger canbe even cooler, thus increasing the combustion efficiency. At the sametime, a low temperature can allow supercharger 100 to go to a higherpressure ratio before reaching the thermal limit of the supercharger.Furthermore, since the air coming into the supercharger 100 is mixedwith the colder air backflowing through conduits 112, the supercharger100 would be able to intake hotter air than the conventionalsupercharger. In other words, the modified supercharger system canimprove the supercharger's capability to handle high temperature inletair.

For example, tolerances can be strategically reduced because the cooledbackflow air prevents the supercharger from attaining a high heat fromthe blowing of intake air. Or, a higher intake air temperature can beaccommodated with customary tolerances because the cooled air will bringthe overall air temperature within normal operating ranges. Since therelationship between thermal expansion tolerances and outlettemperatures is linear, if the outlet temperature is reduced, thetolerances between the rotors can be reduced, and the tolerances betweenthe rotors and housing can be reduced by the same percentage that theoutlet temperature is reduced.

There can be other benefits of using the recirculation conduits 112 inthe supercharger system 10. In the modified system, EGR (exhaust gasrecirculation) handling capability can be improved since the airrecirculated via EGR can be cooled with the backflow air.

Conduits 112 can also improve efficiency of the supercharger 100. Havingconduits 112 can lower the outlet 104 temperature and in turn lower theoverall temperature operation range of the supercharger 100. If theoverall temperature operation range is reduced, then tolerances betweenrotors and the case can be tightened, and thus improve operatingefficiency of the supercharger 100.

The placement of radial flow and axial flow backflow ports 122, 1222 canbe distanced from the inlet 101 and the outlet 104, and rather close torotors 102, 103. The size and shape of the radial flow and axial flowbackflow ports 122, 1222 is designed to optimize cooled air flow fromthe intercooler to in between rotor lobes while minimizing the use ofthe ports as an air outlet. By selecting the dimensions (length, width,height) of the conduits 112, and by virtue of high pressure air movingtowards areas of low pressure, the cooled air moves back towards the hotchamber 105.

FIG. 1B is a schematic of a supercharger system 11 with cooled airbackflow conduits 112 and having an air bypass conduit 115C. The system11 allows air bypass at times when the supercharger's full capacity isnot needed in the combustion engine. So, in periods where limited or noengine boost is desired, air can be bypassed away from the engine 120and returned to the inlet 101 of the supercharger 100. Bypass conduit115C is shown after the intercooler 110, though other locations arepossible. A bypass valve 115A is controlled via bypass actuator 115. Thebypass actuator 115 can comprise a sensor in addition to actuationmechanisms and control electronics to receive commands and emit signalsfor controlling bypass valve open or close parameters.

FIG. 1C is a schematic of a supercharger system 12 with combined airbackflow and bypass conduits. A multi-way valve 116A receives cooled airfrom intercooler outlet 111 via the combined conduit 116B. Actuator 116can comprise a sensor in addition to actuation mechanisms and controlelectronics to receive commands and emit signals for controllingmulti-way valve 116A open or close parameters. Multi-way valve 116A canbe controlled to bypass air in bypass conduit 115C to the inlet 101 ofsupercharger 100. Multi-way valve 116A can also direct cooled air toradial flow backflow ports 122 via conduit 112. While a single valve isillustrated for multi-way valve 116A, alternatives use more than onevalve or additional conduit branching to achieve the bypass and backflowprinciples.

FIGS. 1B and 1C offer control of the backflow event and enableadjustment to the temperature and flow rate at the outlet 104 of thesupercharger 100. That is, the bypass valve 115A or multi-way valve 116Acan be controlled to adjust an intake flow rate by adjusting airsupplied to inlet 101. The backflow event can be adjusted by control ofvalve 114A or multi-way valve 116A. While only radial flow backflowports 122 are illustrated in FIGS. 1A-1C, as above, there can be onlyaxial flow backflow ports 1222, multiple radial flow back flow ports122, or a combination of axial flow and radial flow back flow ports.

FIG. 2A shows a control mechanism 20 for the backflow control system ofFIG. 1A. The control mechanism 20 can be programmed to control thebackflow event to adjust the temperature at the outlet 104 of thesupercharger 100. The control mechanism 20 enables the implementation ofa method for controlling the outlet condition of the supercharger 100through conditioning of the backflow air.

The control mechanism 20 can control air circulation through the system10, allowing some portion of cooled air to backflow to the supercharger100. At times, it may be beneficial to terminate backflow, so thecontrol mechanism 20 can adjust the amount of cooled air from zero up toa maximum amount by controlling actuators 114 affiliated with valves114A. The maximum amount of backflow is calculated and controlled basedon engine air flow demands and temperature requirements, and thus canvary based on operating conditions and from vehicle to vehicle and fromdriver to driver.

The control mechanism 20 can control whether a backflow or bypass eventtakes place. When the supercharger actively blows air to the engine, thecontrol mechanism 20 controls the valves 114A and 116A to provide abackflow event. But when cooling is not needed, or when the superchargeris idling, the control mechanism controls bypass valve 115A and valves114A or valve 116A to bypass air back to the inlet side of thesupercharger. If the air is cooled by the intercooler 110, then thebypassed air can cool the supercharger and the passive (not-blown) airpassing through the system. Because this passive cooling is not alwaysneeded, it is possible to connect the bypass valve 115A prior to theintercooler 110 to bypass uncooled air back in to the system.

Control mechanism 20 can be a part of one or more control mechanismsemployed in a vehicle, such as on-board computers, computing chips, andother processing devices that control vehicle operations. Controlmechanism 20 includes customary non-transient computing elements, suchas transmit and receive ports, processor, memory, and programming.

The control mechanism 20 can be a part of an engine control unit (ECU).The control mechanism 20 can include a controller 150, sensors 151, 152,153, and an actuator 114 that operates valve 114A. The actuator 114 caninclude sensors for collecting data on the opening degree of the valve114A. The number and placement of sensors can vary based on feedbackcontrol implemented, and so the system can have more or less sensors andactuators than in the illustrated example. The sensors can be of avariety of types capable of sensing conditions and of sending signals,such as temperature, pressure, speed, or air flow (velocity). Theillustrated sensors can include a plurality of types, such that a sensorcan measure multiple conditions, such as both temperature and air flow.

The valve 114A can be opened or closed as determined by the controller150 to be appropriate for the vehicle's operation mode. The openingdegree of the valve 114A can range from fully open to fully closed.

The determination of opening/closing the valve 114A can be made bymeasuring the temperature of the air at the outlet 104, or thetemperature in the engine 120. Further, the temperature reading of theair expelling out of the outlet port 111 can also affect the decision toopen/close or to adjust the opening degree of the valve 114A.

The sensor 151 can be a mass air flow sensor (MAF), measuring the massflow rate inside the engine 120. For instance, the sensor 151 can be ahot wire sensor. Sensor 151 can be positioned inside the engine 120. Thereading from the sensor 151 ensures that optimal amount of air is beingsupplied to the engine 120. Sensor 151 can also measure the temperatureinside the engine.

The sensor 152 can be a temperature sensor, measuring the temperature ofthe blown air exiting the outlet 104 of the supercharger 100. The sensor152 can also measure the flow rate of the air. The air blown out fromthe supercharger 100 may need to be sufficiently cooled prior toentering the intake manifold 121. If the air is not sufficiently cooled,then the most power efficient combustion process may not occur in theengine 120. Therefore, the air temperature may need to be reduced by theintercooler 110 to reach the optimal temperature to enable moreefficient and powerful combustion inside the engine 120. By backflowingcooled air to the supercharger 100, the air at the outlet 104 is loweredsignificantly. And, when the temperature of air must be increased forefficient engine operation, the valve 114A can be adjusted to restrictcooled air backflow.

The sensor 153 may be a pressure sensor, measuring the pressure of theair building in the intake manifold 121 of the engine 120. The purposeof the supercharger 100 is to provide a boost to the engine 120,allowing the engine 120 be more powerful. Boost is given in terms ofpressure ratio, which is the ratio of absolute air pressure before thesupercharger to the absolute air pressure after compression by thesupercharger 100. Therefore, it is important to have the appropriatepressure for air entering the intake manifold 121. The pressure sensor153 can be located on the intake manifold 121 of the engine 120 toprovide feedback to controller 150.

The readings from the sensors 114, 151, 152 and 153 are transmitted tothe controller 150. The controller 150 can compare each received readingfrom the sensors 114, 151, 152, and 153 with predetermined values. Thepredetermined values can be calculated optimal values that have beensaved in the control system, or the predetermined values can becalculated in real time based on vehicle dynamics.

For example, the reading from the sensor 151 can be equal to apredetermined value. That means that the current air amount going intothe engine and air entering into the supercharger is optimal. Therefore,if the controller 150 determines that the reading from the sensor 151 isequal to the predetermined value, then no action may be taken. On theother hand, the reading from the sensor 151 may not be equal to thepredetermined value. That means that the current flow rate ortemperature of air, either going into the engine or exiting thesupercharger, is not optimal. In this case, the controller 150 can emita signal to either open or close valves 114A using actuators 114, amongother adjustment signals. By opening or closing valves 114A, thetemperature of the supercharger can be adjusted. By controlling the hebackflow event, outlet pressure pulsations can be influenced dependingon the desired results. Additional control mechanisms can be implementedto adjust the speed of the supercharger 100, among other operatingconditions. Similar determinations and adjustments can be made for theremaining sensors.

The controller 150 can adjust an amount of air in conduit 112 bycontrolling the opening degree of the valve 114A. Similarly, thecontroller 150 can adjust other operating conditions, such as an openingdegree of a throttle valve. By having the appropriate amount of aireither in backflow or entering the supercharger 100, the efficiency ofthe supercharger system 10 can be ensured.

Alternative control mechanisms 21 and 22 are shown in FIGS. 2B and 2C.Control mechanism 21 corresponds to system 11 of FIG. 1B. Similar tothat outlined for FIG. 2A, the controller 150 of FIG. 2B can adjust thebackflow event. The system 11 can also send signals to bypass actuator115 to control the amount of air bypassed away from engine 120. Thisenables more control over the amount of air entering supercharger 100.

FIG. 2C likewise controls multi-way actuator 116 of multi-way valve 116Ato tailor the amount of cooled air bypassed to the inlet 101 or providedto radial flow backflow ports 122 and/or axial flow backflow ports 1222.

Engine air flow demand can be based on a variety of other vehicleoperating conditions, so, in addition to comparisons to predeterminedvalues, or alternatively thereto, calculations can take place in realtime. The simplified control mechanisms of FIGS. 2A, 2B, and 2C can thusbe augmented to include additional sensors and feedback and can be tiedto other vehicle controls, such as acceleration, yaw, rollover, slip,braking, etc. Thus, as engine air flow demands change due to these otherfactors, the cooled air backflow and bypass events can be adjusted totailor air temperature at outlet 104.

Experiments were conducted to test the effect of the backflow of cooledair at 14,000 RPM. The results obtained in these experiments will be nowexplained using FIG. 3. The graph in FIG. 3 shows the relationshipbetween the temperatures at supercharger outlet 104 with the pressureratio achievable. FIG. 3 graphs experimental data conducted at a speedof 14,000 RPM. The vertical axis indicates the temperature ofsupercharger outlet 104 while the horizontal axis indicates pressureratio. In doing the experiment, the thermal limit was set to 150° C. Thethermal limit, or maximum operating temperature, is one of theparameters for determining the pressure ratio of a Roots typesupercharger. If one increases the pressure supplied by the superchargerwithout increasing the temperature of the supplied air, thensignificantly higher pressure ratio can be reached. The inlettemperature was constant at 27° Celsius. The supercharger used in theexperiment was an M45 Roots type supercharger manufactured by EatonCorporation, like the example shown in FIG. 5.

The graphs show data for the pressure ratio for the M45 superchargerwithout cold air backflow, and the pressure ratio for the M45supercharger with cold air backflow. The resulting graph line for theM45 supercharger without cold air backflow is inclined to about 45degrees, more sharply than with cold air backflow.

The results indicate that a higher pressure ratio for the given thermallimit occurs in the M45 supercharger with cold air backflow. FIG. 3shows that at 150° Celsius, the pressure ratio for the M45 without coldair backflow was 2.2. To achieve a pressure ratio higher than 2.2, thesupercharger must be run beyond its thermal limit, which is notpractical because of the thermal expansion of parts and interferencewith tolerances. However, by having the cold air backflow in the M45supercharger, the pressure ratio increases to about 4.5 withoutexceeding the thermal limit.

In addition to the experiment testing the effect of cooled backflow airon pressure ratio, the effect of backflow on temperature was simulated.Comparing FIGS. 4A and 4B shows the effect of the cooled air on thetemperature of the air at the outlet of the supercharger. The simulationwas conducted at the supercharger speed of 6000 RPM. FIG. 4A shows thesimulation results of the temperature distribution in the superchargersystem without the cold air backflow. Air enters the supercharger 100Xand is heated and expelled towards intercooler 110X. A backflow conduit122Y allows expelled air to enter port 122X. The air is heated via thepumping action of supercharger 100X, so the expelled air is hot comparedto the inlet temperature. The temperature distribution (K) within thesupercharger system was simulated with given constants which include apressure ratio of 2 and an inlet temperature of 300K. When measured, theoutlet temperature was close to 435K, resulting in a temperatureincrease of 135K from inlet to outlet.

On the other hand, the supercharger system with cooled air backflow inFIG. 4B showed less temperature increase. Air entered supercharger 100and was expelled to intercooler 110. After exiting the intercooler,cooled air travelled through conduit 112 to backflow in to supercharger100. The outlet temperature was 388K, and thus, the net temperatureincrease was only 88K from inlet to outlet. Therefore, the backflow ofcold air in the supercharger system reduced the temperature of the airat the outlet of the supercharger.

FIG. 5 shows a model of supercharger 100 that can be used in thesupercharger systems 10, 11, and 12. Supercharger 100 is an axial inlet,radial outlet type. An air flow path is shown by arrows so that airentering an air inlet on the right side of the page exits out atriangular outlet 104 in the center of the page. A portion of the outerhousing is removed to show inside main case 106. Supercharger 100 canbe, for example, an M45 or other Roots type supercharger manufactured byEaton Corporation, including its TVS® brand Twin Vortices Series type.FIG. 5 shows the cross section of the supercharger 100 having multipleradial flow backflow ports 122 communicating with each rotor.Supercharger 100 has two rotors 102, 103 having three lobes. Two rotors102, 103 are placed in the housing chamber 105. Radial flow backflowports 122 can be placed on each side of the outlet and near each rotor102, 103. By placing the radial flow backflow ports 122 to direct airbetween adjacent lobes of each rotor, the cooled air can be effectivelymixed with the intake air to lower the temperature of the air beingtransported out of the supercharger 100.

Radial flow backflow ports 122 and or axial flow backflow ports 1222 canbe placed in the main case 106 of the tubular housing to interface withrecirculation conduits 112. Main case 106 can be formed as a castingdefining the inlet port 101, outlet port 104, and radial flow 122 and oraxial flow backflow ports 1222. Main case 106 can comprise multiplesections integrated together, and main case 106 can be integrated withother housing sections to form an air envelope around the rotors, rotormounts, gear case, and other operational features of supercharger 100.

The aspects detailed above for FIGS. 1A-10 are applicable to the thermalabatement systems below. FIGS. 11A-13B illustrate that the combustionprocess can be tuned for efficiency. Tuning the temperature of airflowing in a combustion system provides many benefits, such as fuelefficiency, efficient particulate filtering, and enhanced drivability ofa motive device affiliated with such thermal abatement. FIGS. 11A-13Bdetail alternative thermal abatement systems with various flow paths forback flow of intercooled air, various optional and alternative uses ofhigh or low pressure exhaust gas recirculation, and various aircompression strategies. The alternative arrangements detailed above forbypass control, backflow control, conduit or manifold tuning, etc. applyequally to FIGS. 11A-13B.

FIGS. 11A-13B illustrate thermal abatement systems comprising an axialinlet, radial outlet supercharger. The main case 106 of the supercharger100 is as described above, and comprises, for example, one to three setsof back ports, which can be one or both of axial flow back flow ports1222 and radial flow back flow ports 122. One of intercoolers 110, 210and 410 is connected to receive air, to cool the received air, and toexpel the cooled air to the at least two back flow ports. Atmosphericair enters the main inlet 2000 to the thermal abatement systems. Inaddition to the back flow provided by conduits 112 & 112A-112C, the airis also compressed, cooled, optionally mixed with exhaust gasrecirculation (EGR) gases via EGR conduits 3001 & 3003 and relatedports, combusted by engine 120, and exhausted out main outlet 2001.Above line 2003, the air intake system is described, while below line2003, the exhaust system is described. Computer control of the selectivesystems is outlined in FIGS. 2D-2F.

When the optional EGR strategies are implemented, various factors assistthe induction and pressurized action of the EGR gas. It is possible torely on pressure differences, aspiration, thermal gradients, etc. toroute the EGR gas for further combustion. Various control strategies canthus be implemented to selectively route the EGR gas, as by valves andactuators controlled via feedback loops with sensors and processorimplemented algorithms.

FIGS. 11A-11D illustrate thermal abatement systems wherein asupercharger boosts air, which is further boosted by a turbocharger.FIG. 11A shows a first alternative where air from the main inlet 2000enters the supercharger 100, is output to intercooler 110 for cooling,is further compressed by turbocharger compressor 200C and cooled byintercooler 210. A backflow conduit 112A selectively provides cooled airfrom intercooler 210 to the backflow ports of supercharger 100.

An engine 120 is connected to receive the expelled cooled air from theintercooler 210 and further connected to expel exhaust. An EGR conduit3001 is connected to selectively receive a portion of the expelledexhaust, as by computer control of an EGR valve 118A via EGR actuator118. The optional EGR conduit 3001 is connected to an optional EGR input3001D to return the received portion of the exhaust to the inlet of thesupercharger 100. A remaining portion of the exhaust passes through theturbine 200T of the turbocharger. The exhaust spins the turbine 200T,which is connected to operate the compressor 200C. The exhaust exits themain outlet 2001 of the thermal abatement system.

Because the EGR conduit 3001 is prior to the turbine 200T, abackpressure can be created, as by control of an exhaust valve, or as bythe action of the turbine 200T. The exhaust gas selected for EGR isconsidered “high pressure” because of the increase in pressure on theexhaust caused by the back pressure. Instead of inputting the EGR priorto the supercharger 100, other locations are suitable, such asalternative EGR input 3001E.

Many control strategies and alternative layouts are possible. Forexample, it is possible to selectively power supercharger 100 fordesired boost conditions. For no or very low boost conditions, it ispossible to run only one of supercharger 100 or turbine 200C, but tooperate both supercharger 100 and compressor 200C for high boostconditions. The intercoolers 210 and 110 are also alternatively appliedto cool the air so that only one or both are used based on conditions.

FIG. 11C shows a “low pressure” alternative to FIG. 11A. EGR gas isselectively diverted back for combustion after it exits the turbine200T. Because there is little to no backpressure on the exhaust prior tothe main outlet 2001, the EGR gas is directed to the atmosphericpressure or low pressure inlet 101 of supercharger 100 via EGR input3003D.

FIG. 11B shows an alternative aspect for a supercharger boosting air toa turbocharger in a thermal abatement system. Aspects of FIG. 11B thatare similar to FIG. 11A are not repeated. But, the back flow conduit 112is connected between intercooler 110 and supercharger 100. Theturbocharger compressor 200C supplies compressed air to intercooler 210,and the cooled air from intercooler 210 can directly supply air forcombustion in engine 120. As above, pre-engine bypass of compressed airis possible at any point prior to the air reaching the combustioncylinders of engine 120. High pressure EGR is possible between EGRconduit 3001 and either of EGR inputs 3001D or 3001E.

FIG. 11D is a low pressure alternative aspect of FIG. 11C. Bypass andback flow alternatives remain as above, but by connecting EGR conduit3003 after the turbine, there is little to no backpressure on theexhaust prior to the main outlet 2001. The low to atmospheric pressureof the EGR gas is directed to the atmospheric pressure or low pressureinlet 101 of supercharger 100 via EGR input 3003D.

Turning to FIG. 12A, a thermal abatement system implements aturbocharger fed supercharger. Atmospheric air is brought in main inlet2000, where the compressor 200C of the turbocharger compresses the air.An optional intercooler 210 cools the compressed air, and it isconnected to the inlet of supercharger 100. The supercharger blows theair to intercooler 110 and a portion of the cooled air is selectivelydirected via backflow conduit 112 to backflow ports in supercharger 100.Bypass and computer control of valve opening and closing are present.

Cooled air for combustion is directed from intercooler 110 to engine120. Engine 120 expels exhaust to power the turbine 200T of theturbocharger and exhaust exits the main outlet 2001.

Optionally, the system of FIG. 12A comprises EGR conduit 3001. Becauseit is placed between the engine and turbine, the EGR gas is subject tobackpressure and or valve control to create “high pressure” EGR.Alternative EGR ports 3001A and 3001B permit EGR gas to be inserted backin to the system before or after the optional intercooler 210.

Many control strategies and alternative layouts are possible. Forexample, it is possible to selectively power supercharger 100 fordesired boost conditions. For no or very low boost conditions, it ispossible to run only one of supercharger 100 or turbine 200C, but tooperate both supercharger 100 and compressor 200C for high boostconditions. The intercoolers 210 and 110 are also alternatively appliedto cool the air so that only one or both are used based on conditions.

FIG. 12B is an alternative aspect of FIG. 12A using “low pressure” EGR.The EGR conduit 3003 is attached after the turbine 200T, and the low tono pressure exhaust gas can be routed for further combustion to any oneof alternative EGR ports 3003A, 3003B, or 3003C.

FIG. 13A shows a thermal abatement system having a supercharger 400 fedby another supercharger 100. Air enters main inlet 2000 and is blown orpassed through supercharger 100. The air then enters intercooler 410where it is cooled prior to use or passage through supercharger 400.Another intercooler 110 is connected to provide further cooling prior toentry to engine 120. A selective portion of cooled air from intercooler110 is routed via backflow conduit 112B to supercharger 100 backflowports.

Many control strategies and alternative layouts are possible. Forexample, it is possible to power only one of the superchargers 400 or100 for low boost conditions and to power both superchargers 400 and 100for high boost conditions. The intercoolers 410 and 110 are alsoalternatively applied to cool the air so that only one or both are usedbased on conditions. Because supercharger 400 is not connected tobackflow conduits, it is possible to use a simplified supercharger withno backflow ports, thus providing a second source of boost whileminimizing outlay costs.

FIG. 13A optionally includes EGR conduit 3003 to selectively routeexhaust for EGR. The EGR gas can be inserted for further combustion viaany one of EGR ports 3003F, 3003G, & 3003H.

FIG. 13B shows an alternative aspect of FIG. 13A. Both supercharger 400and supercharger 100 are designed to receive backflow from theirrespective intercoolers. Thus, intercooler 410 cools air, and aselective quantity of cooled air is connected via backflow conduit 112Cto the backflow ports of supercharger 100. Likewise, intercooler 110cools air, and a selective quantity of cooled air is connected viabackflow conduit 112 to the backflow ports of supercharger 400.

Much like above for FIGS. 2A-2C, computer-implemented control forselecting the quantity and timing of backflow, bypass, and EGR ispossible for FIGS. 11A-13B. Examples are shown in FIGS. 2D-2F.

The control mechanisms 24, 25, & 26 can be a part of an engine controlunit (ECU), as explained above for control mechanisms 20-23. The controlmechanisms 24-26 can include a controller 150, sensors 151, 152, 153,actuator 114 that operates valve 114A, and actuator 118 that operatesvalve 118. The actuators 114 & 118 can include sensors for collectingdata on the opening degree of their affiliated valves. Additionaloptions for using bypass actuator 115 and multi-way actuator 116 areillustrated, and implementation of their affiliated valves 115A & 116Aare as above.

The number and placement of sensors can vary based on feedback controlimplemented, and so the system can have more or less sensors andactuators than in the illustrated example. For example, sensors 156 &158 are shown in broken lines to indicate that they are optional andalternative depending upon application. If sensor 151 can senseinformation adequate to determine whether to implement EGR, such asexhaust quantity and flow rate, then an additional exhaust sensor maynot be needed. But, it is possible to include one or more sensorcapabilities in the exhaust flow path, to determine whether to implementEGR.

Like above, sensors 156 & 158 can be of a variety of types capable ofsensing conditions and of sending signals, such as temperature,pressure, speed, or air flow (velocity). The illustrated sensors caninclude a plurality of types, such that a sensor can measure multipleconditions, such as both temperature and air flow.

The addition of the EGR valve 118A and actuator 118 permit furthertailoring of temperature, pressure, fuel efficiency, etc. by permittingexhaust gas to recirculate. Selective heating and cooling of thecombustion process thereby enhances compliance with CAFE fuelrequirements, permits efficient charcoal canister use, and the otherbenefits detailed above.

In the preceding specification, various aspects of the present teachingshave been described with reference to the accompanying drawings. Itwill, however, be evident that various other modifications and changesmay be made thereto, and additional aspects may be implemented, withoutdeparting from the broader scope of the claims that follow. Thespecification and drawings are accordingly to be regarded in anillustrative rather than restrictive sense.

Other aspects of the present teachings will be apparent to those skilledin the art from consideration of the specification and by practice ofthe disclosure. For example, it is possible to have a main engineintercooler, such as intercooler 110, and additional intercoolersdedicated to each backflow conduit 112 or backflow port 122. It isintended that the specification and examples be considered as exemplaryonly, with the true scope of the invention being indicated by thefollowing claims.

We claim:
 1. An axial inlet, radial outlet supercharger, comprising: atubular housing, the tubular housing comprising: an inlet wall; an inletthrough the inlet wall, the inlet configured to direct inlet airparallel to an inlet axis; an outlet configured to emit the inlet airperpendicular to the inlet axis; two rotor mounting recesses in an innersurface of the inlet wall, the inlet axis being between the two rotormounting recesses; and at least two axial flow backflow ports throughthe inlet wall.
 2. The supercharger of claim 1, wherein each of the atleast two axial flow backflow ports is a slot having a profile matchinga segment on an involute curve.
 3. The supercharger of claim 1, whereinthe tubular housing further comprises at least two radial flow backflowports.
 4. The supercharger of claim 3, wherein each of the at least twoaxial flow backflow ports and each of the at least two radial flowbackflow ports is one of a rectangular slot, an oval hole, a circularhole, or a slot having four sides, each of the four sides being an arcof a circle.
 5. The supercharger of claim 1, further comprising a frontplate separated from the inlet wall by a tuning distance.
 6. Thesupercharger of claim 5, further comprising a pass-through in the frontplate, the pass-through aligning with each of the at least two axialflow backflow ports.
 7. The supercharger of claim 6, further comprisinga recirculation conduit coupled to the pass-through.
 8. The superchargerof claim 5, further comprising a floor between the inlet wall and thefront plate, the floor fluidly separating the inlet from the at leasttwo axial flow backflow ports.
 9. The supercharger of claim 8, furthercomprising a support in the inlet, the support abutting the floor. 10.The supercharger of claim 1, wherein the axial flow backflow portsoccupy up to a backflow port area A_(Port) in the tubular housingdetermined by:$A_{Port} = \frac{\frac{\left( {{\frac{P_{2}}{{RT}_{2}}V_{TransferVolume}} - {\frac{P_{1}}{{RT}_{1}}V_{TransferVolume}}} \right)}{\left( {\frac{{Angle}\mspace{14mu}{for}\mspace{14mu}{{Backflow} \times 60}}{360}/N_{RPM}} \right)}}{\frac{P_{2}}{{RT}_{2}}\frac{a_{1}}{\gamma}\left( {\frac{P_{2}}{P_{1}} - 1} \right)\left( \frac{\frac{2\gamma}{\gamma + 1}}{\frac{P_{2}}{P_{1}} + \frac{\gamma - 1}{\gamma + 1}} \right)^{\frac{1}{2}}}$where P₁ is an inlet pressure, P₂ is a maximum pressure ratio of theoutlet, T₁ is an inlet temperature, T₂ is an outlet temperature, R is agas coefficient, N_(RPM) is a maximum speed in rotations per minute ofrotors in the supercharger, V_(TransferVolume) is a volume of airtransferred, a is a speed of sound at a given inlet temperature T₁, γ isa ratio of specific heat at a constant pressure and constant volume. 11.The supercharger of claim 10, wherein the axial flow backflow portsoccupy an ideal port area A_(IPort) in the range of one fourth to fourtimes the backflow port area A_(Port).
 12. The supercharger of claim 11,wherein the ideal port area A_(IPort) is one half to two times thebackflow port area A_(Port).
 13. The supercharger of claim 11, whereinthe ideal port area A_(IPort) is two thirds of the backflow port areaA_(Port).
 14. The supercharger of claim 10, further comprising at leasttwo radial flow backflow ports, the backflow port area A_(Port) furthercomprising the area occupied by the at least two radial flow backflowports.
 15. The supercharger of claim 10, further comprising at least tworadial flow backflow ports, wherein the ideal port area A_(IPort) isfurther occupied by the radial flow backflow ports.
 16. The superchargerof claim 1, wherein a first of the two rotor mounting recess recessescomprises a center point on the inlet wall, wherein an inlet area of onehalf of the inlet occupies a span about the center point of 80-200degrees of the inlet wall, and wherein a first of the at least two axialflow backflow ports occupies a span about the center point of 10-40degrees of the inlet wall.
 17. The supercharger of claim 16, wherein thefirst of the at least two axial flow backflow ports occupies a spanabout the center point of 10-15 degrees of the inlet wall.
 18. Thesupercharger of claim 16, wherein the first of the at least two axialflow backflow ports occupies a span about the center point of 30-40degrees of the inlet wall.
 19. The supercharger of claim 16, wherein theinlet area is separated by a span about the center point of 82-190degrees from the first of the at least two axial flow backflow ports.20. The supercharger of claim 16, wherein the inlet area is separated bya span about the center point of 100-170 degrees from the first of theat least two axial flow backflow ports.
 21. The supercharger of claim16, wherein a second of the two rotor mounting recesses comprises asecond center point on the inlet wall, wherein a second inlet area ofthe second half of the inlet occupies a span about the second centerpoint of 80-200 degrees of the inlet wall, and wherein a second of theat least two axial flow backflow ports occupies a span about the secondcenter point of 10-40 degrees of the inlet wall.
 22. The supercharger ofclaim 1, comprising: lobed rotors comprising lobes, each lobed rotorcomprising a rotation axis parallel to the inlet axis, wherein the lobessequentially mesh along the inlet axis when the rotors rotate, whereinrespective lobes are twisted along the length of their respective rotor,and wherein the lobes are timed to fluidly seal the inlet from theoutlet.
 23. The supercharger of claim 22, further comprising at leasttwo radial flow back flow ports on either side of the outlet.
 24. Thesupercharger of claim 22, wherein each lobed rotor rotates to move alobe on the rotor, and the lobe rotates 210-280 degrees to complete aninlet phase, and the lobe rotates 0-50 degrees to complete a dwellphase, and the lobe rotates 15-70 degrees to complete a seal phase, andthe lobe rotates 20-70 degrees to complete a backflow phase, and whereinthe lobe rotates 200-220 degrees to complete an outlet phase.
 25. Thesupercharger of claim 22, wherein each lobed rotor rotates to move alobe on the rotor, and the lobe rotates 210-280 degrees to complete aninlet phase, and the lobe rotates 20-50 degrees to complete a dwellphase, and the lobe rotates 10-50 degrees to complete a seal phase, andthe lobe rotates 20-80 degrees to complete a backflow phase, and whereinthe lobe rotates 200-220 degrees to complete an outlet phase.
 26. Thesupercharger of claim 22, wherein each of the at least two axial flowbackflow ports are shaped to open in 10 to 15 degrees of lobe rotation.27. The supercharger of claim 22, wherein each of the at least two axialflow backflow ports are shaped to open in 30 to 40 degrees of loberotation.
 28. The supercharger of claim 22, wherein each of the at leasttwo axial flow backflow ports are shaped to open in 10 to 40 degrees oflobe rotation.
 29. The supercharger of claim 22, wherein the at leasttwo axial flow backflow ports are sized to be fully blocked byrespective lobes when the lobes rotate in front of respective ones ofthe at least two axial flow backflow ports.
 30. The supercharger ofclaim 22, wherein the supercharger has a thermal limit of 150 degreesCelsius and an outlet pressure to inlet pressure pressure ratio of4.4:1.
 31. The supercharger of claim 22, wherein the respective lobesare twisted along the length of their respective rotor from 60-150degrees.
 32. The supercharger of claim 22, wherein the each one of thelobed rotors comprises three lobes, four lobes, or five lobes.
 33. Thesupercharger of claim 22, wherein each lobe has a profile, and whereineach of the at least two axial flow backflow ports are shaped assegments of the lobe profile.
 34. The supercharger of claim 1, furthercomprising: an intercooler comprising an inlet and an outlet, theintercooler connected to receive blown air from the outlet of thesupercharger and connected to cool and expel the received air asbackflow air; and conduits connecting the axial flow backflow ports ofthe supercharger to the outlet of the intercooler to receive thebackflow air.
 35. The supercharger of claim 34: wherein the first rotorcomprises at least a first lobe and a second lobe, wherein the secondrotor comprises at least a third lobe and a fourth lobe, wherein the atleast two axial flow backflow ports comprise a first backflow port and asecond backflow port, wherein the first backflow port is sealed by thefirst lobe when backflow air is exposed to the second backflow port andto a gap between the third lobe and the fourth lobe, and wherein thesecond backflow port is sealed by the fourth lobe when the backflow airis exposed to the first backflow port and to a second gap between thefirst lobe and the second lobe.
 36. The supercharger of claim 34,wherein the supercharger further comprises at least two radial flow backflow ports, and wherein the conduits further connect the radial flowback flow ports to the outlet of the intercooler.
 37. The superchargerof claim 34, wherein the lobed rotors comprise a first rotatable rotorand a second rotatable rotor, wherein each of the first rotor and thesecond rotor comprise at least three lobes, wherein a respective gap isformed between each adjacent lobe, wherein, when a gap is aligned, thebackflow ports are oriented to provide cooled air from the intercoolerto an adjacent gap, and wherein the adjacent gap is sealed from theinlet and from the outlet when the cooled air is provided to theadjacent gap.
 38. An axial inlet, radial outlet supercharger,comprising: a tubular housing, the tubular housing comprising: an inletwall; an inlet through the inlet wall, the inlet configured to directinlet air parallel to an inlet axis; an outlet configured to emit theinlet air perpendicular to the inlet axis; two rotor mounting recessesin an inner surface of the inlet wall, the inlet axis being between thetwo rotor mounting recesses; at least two backflow ports in the tubularhousing; lobed rotors, each lobed rotor comprising a rotation axisparallel to the inlet axis, wherein the lobes sequentially mesh alongthe inlet axis when the rotors rotate, wherein respective lobes aretwisted along the length of their respective rotor, and wherein thelobes are timed to fluidly seal the inlet from the outlet; anintercooler comprising an inlet and an outlet, the intercooler connectedto receive blown air from the outlet of the supercharger and connectedto cool and expel the received air as backflow air; and conduitsconnecting the at least two backflow ports of the supercharger to theoutlet of the intercooler to receive the backflow air, wherein the firstrotor comprises at least a first lobe and a second lobe, wherein thesecond rotor comprises at least a third lobe and a fourth lobe, whereinthe at least two backflow ports comprise a first backflow port and asecond backflow port, wherein the first backflow port is sealed by thefirst lobe when backflow air is exposed to the second backflow port andto a gap between the third lobe and the fourth lobe, and wherein thesecond backflow port is sealed by the fourth lobe when the backflow airis exposed to the first backflow port and to a second gap between thefirst lobe and the second lobe.
 39. An axial inlet, radial outletsupercharger, comprising: a tubular housing, the tubular housingcomprising: an inlet wall; an inlet through the inlet wall, the inletconfigured to direct inlet air parallel to an inlet axis; an outletconfigured to emit the inlet air perpendicular to the inlet axis; tworotor mounting recesses in an inner surface of the inlet wall, the inletaxis being between the two rotor mounting recesses; at least twobackflow ports in the tubular housing; an intercooler comprising aninlet and an outlet, the intercooler connected to receive blown air fromthe outlet of the supercharger and connected to cool and expel thereceived air as backflow air; and conduits connecting the at least twobackflow ports of the supercharger to the outlet of the intercooler toreceive the backflow air, wherein the outlet is in the tubular housing,wherein the at least two backflow ports comprise radial flow back flowports in the tubular housing, and wherein the conduits further connectthe radial flow back flow ports to the outlet of the intercooler. 40.The axial inlet, radial outlet supercharger of claim 39, furthercomprising lobed rotors, each lobed rotor comprising a rotation axisparallel to the inlet axis, wherein the lobes sequentially mesh alongthe inlet axis when the rotors rotate, wherein respective lobes aretwisted along the length of their respective rotor, and wherein thelobes are timed to fluidly seal the inlet from the outlet.
 41. The axialinlet, radial outlet supercharger of claim 40, wherein the lobed rotorscomprise a first rotatable rotor and a second rotatable rotor, whereineach of the first rotor and the second rotor comprise at least threelobes, wherein a respective gap is formed between each adjacent lobe,wherein, when one of the respective gaps is aligned with one of the atleast two backflow ports, cooled air from the intercooler is provided tothe one respective gap, and wherein the one respective gap is sealedfrom the inlet and from the outlet when the cooled air is provided tothe one respective gap.
 42. The axial inlet, radial outlet superchargerof claim 40, wherein the first rotor comprises at least a first lobe anda second lobe, wherein the second rotor comprises at least a third lobeand a fourth lobe, wherein the at least two backflow ports comprise afirst backflow port and a second backflow port, wherein the firstbackflow port is sealed by the first lobe when backflow air is exposedto the second backflow port and to a gap between the third lobe and thefourth lobe, and wherein the second backflow port is sealed by thefourth lobe when the backflow air is exposed to the first backflow portand to a second gap between the first lobe and the second lobe.
 43. Anaxial inlet, radial outlet supercharger, comprising: a tubular housing,the tubular housing comprising: an inlet wall; an inlet through theinlet wall, the inlet configured to direct inlet air parallel to aninlet axis; an outlet configured to emit the inlet air perpendicular tothe inlet axis; two rotor mounting recesses in an inner surface of theinlet wall, the inlet axis being between the two rotor mountingrecesses; at least two backflow ports in the tubular housing; anintercooler comprising an inlet and an outlet, the intercooler connectedto receive blown air from the outlet of the supercharger and connectedto cool and expel the received air as backflow air; and conduitsconnecting the at least two backflow ports of the supercharger to theoutlet of the intercooler to receive the backflow air, wherein the atleast two backflow ports comprise axial flow back flow ports in theinlet wall, and wherein the conduits further connect the axial flow backflow ports to the outlet of the intercooler.
 44. The supercharger ofclaim 38, wherein the outlet is tubular housing, and wherein the atleast two backflow ports comprise radial flow back flow ports in thetubular housing and axial flow back flow ports in the inlet wall, andwherein the conduits further connect the radial flow back flow ports andthe axial flow backflow ports to the outlet of the intercooler.